Danfoss RET MD Data sheet
Datasheet
RET MD Intelligent Room Thermostat
Features
RET-M series of room thermostats combine the
ease of use of a setting dial with accuracy and
advanced features, including LCD display, that
are only available from micro-processor based
controller. The LCD display, that normally shows
actual room temperature, changes momentarily
to show set temperature whenever the setting dial
is moved. Styled upon the RET room thermostat,
the RET-M series can be set up by the installer to
provide either traditional on/o control or more
sophisticated chrono-proportional control for
increased comfort and economy.
If set in chrono-proportional mode, the thermostat
imposes a xed cycle rate on the system and then
determines the duration of the On and O periods
within each cycle in proportion to load. The
control algorithm used to determine the on/o
periods uses a proportional + integral (PI) routine
to eliminate oset normally associated with on/o
or simple proportional control.
Chrono-proportional control also signicantly
improves comfort and generally improves boiler
eciency by reducing mean water temperature.
The RET-MD is an intelligent room thermostat
that incorporates an energy saving delay start
feature, which delays the start-up of the heating
dependent upon how close to set-point the room
temperature is at the time heating time switch is
scheduled to turn on the heating system.
Under most load conditions, this feature reduces
the number of hours per day that the system runs,
without creating any discomfort. This feature can,
if necessary, be cancelled if the user wishes to
override the delay period.
A version without delayed start, type RET-M, is also
available. This model oers all the features of the
battery powered RET-B but is mains powered.
Both models are ideal for use with combination
boilers and can be installed without the need for
complicated wiring or commissioning.
Intelligent heating control for increased fuel
economy.
Micro-processor accuracy.
Setting dial with LCD temperature display.
Wallplate construction for ease of installation.
Installer Settings
RET-MD with Delay Start
Sw. Setting Function
1
2
3
4
or 1
2
3
4
or 1
2
3
4
* Change to disable
© Danfoss HS | 09/2015 | 608v03 VDRKE202
Delay Start enabled*
On/O
Not active
°C (change for °F)
Delay Start enabled*
Chrono
3 cycles per hour
°C (change for °F)
Delay Start enabled*
Chrono
6 cycles per hour
°C (change for °F)
Set for cooling operation Set for heating operation
RET-M (no Delay Start Feature)
Sw. Setting Function
1
2
3
4
or 1
2
3
4
or 1
2
3
4
Cool
No compressor delay
Not active
°C (change for °F)
Cool
Compressor delay active
2 min compressor delay
°C (change for °F)
Cool
Compressor delay active
4 min compressor delay
°C (change for °F)
Sw. Setting Function
1
2
3
4
or 1
2
3
4
or 1
2
3
4
Heat
On/O
Not active
°C (change for °F)
Heat
Chrono
3 cycles per hour
°C (change for °F)
Heat
Chrono
6 cycles per hour
°C (change for °F)
1
Datasheet
45.0
Time delay after time control switch-on, minutes
ErP
4
RET MD Intelligent Room Thermostat
Specication and
Ordering Details
ErP Class
Features RET-MD RET-M
Code No 087N726200 087N726400
Temperature Range 5 - 30°C
Setting knob and LCD display
Delay start feature dependent upon proximity to set-point
Delay start override button and LED status indicator
Chrono-proportional or On/O control
Heat or cool operation, including compressor delay timer
Selectable Fahrenheit or Centigrade scaling
Delay start select / disable feature
Output relay contact rating 10-250 Vac, 50/60 Hz, 3 (1) A
Switching action 1 SPDT
Power supply 230 Vac ± 10%, 50/60 Hz
Maximum ambient temperature 45°C
Dimensions (mm) 85 wide x 86 high x 42 deep
(1) Compressor delay only available if thermostat is set to cool operation.
(1)
ERP Class
The products represented within this document are classied according to, and allow completion of, the Energy
Related Product (ErP) Directive System Package che and the ErP system data label. ErP Labelling obligation is
applicable from 26th September 2015.
ErP Class Product Function and ErP Description
TPI Room Thermostat, for use with on/off output heaters
An electronic room thermostat that controls both thermostat
cycle rate and in-cycle on/o ratio of the heater proportional
IV
to room temperature. TPI control strategy reduces mean water
temperature, improves room temperature control accuracy and
enhances system eciency.
Product
Class
Additional eciency
gain
2%
Delay Curve
Wiring
The RET-MD intelligent room thermostat delays the
start-up of the heating system by a variable time
period that is determined by the dierence in the
room temperature compared to the temperature
set on the thermostat. The smaller the dierence,
the longer the delay before the heating is allowed
to turn on. A built-in limit ensures that the delay
period cannot exceed 45 minutes.
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
0.0 1.0
RET-MD RET-M
NO
3
4
ON
N
N L
ELECTRONICS
L
NC
1
2
OFF
COM
3.0 4.0 5.0
2.0
Temperature below thermostat setting, °K
NC
ELECTRONICS
1
N
N L
L
2
COM
Input from Time Control
Danfoss Ltd.
Ampthill Road
Bedford MK42 9ER
Tel: 01234 364621
Fax: 01234 219705
Email: ukheating@danfoss.com
Website: www.heating.danfoss.co.uk
Danfoss can accept no responsibility for possible errors in catalogues, brochures, and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products already
on order provided that such alterations can be made without subsequential changes being necessary in specifications already agreed.
All trademarks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.
3
OFF
6.0 7.0
NO
4
ON
2
© Danfoss HS | 09/2015 | 608v03 VDRKE202
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